Vitamin D3 is a vitamin involved in various functions including metabolism and homeostasis maintenance of calcium and phosphorus, and bone formation, and is produced from cholesterol in the human body. However, because the quantity of vitamin D3 produced in the body is smaller than the required quantities, vitamin D3 needs to be ingested through food, drug products, or supplements.
Vitamin D3 contained in drug products and supplements is produced mainly through ultraviolet irradiation of 7DHC produced by chemical transformation from cholesterol obtained from wool. However, use of animal-derived materials as source materials of drug products and supplements tends to be avoided due to the concerns of BSE and zoonosis, and there is a need for vitamin D3 derived from non-animal. Vitamin D3 derived from non-animals can be produced through ultraviolet irradiation of 7DHC derived from non-animal.
Generally, a sterol biosynthesized by microorganisms is ergosterol. However, some members of Labyrinthulea microorganisms are known to biosynthesize cholesterol (Non-Patent Documents 1 to 3). 7DHC is converted into cholesterol by 7DHC reductase. However, although the Labyrinthulea microorganisms accumulate cholesterol, there is no report that Labyrinthulea microorganisms accumulate 7DHC.
Sterol 24-C-methyltransferase has an activity to introduce a methyl group at the 24-position of a steroid backbone of zymosterol (hereinafter referred to as “sterol 24-C-methyltransferase activity” or “SMT activity”). The SMT activity is essential for the biosynthesis of ergosterol, but is not involved in the biosynthesis of cholesterol.
Further, there is no report that Labyrinthulea microorganisms which biosynthesize cholesterol have SMT activity, and produce and accumulate 7DHC by reducing or eliminating the SMT activity.